Effect of confinement on power-law fluid flow past a circular cylinder

Abstract

The role of confinement on the flow of power-law fluids past a cylinder confined symmetrically between two parallel walls has been investigated numerically over wide ranges of conditions as follows: power-law index (0.4 ≤ n ≤ 1.8), Reynolds number (40 ≤ Re ≤ 140) and blockage ratio (2,4,6). For Newtonian fluids, moderate degree of confinement stabilizes the flow thereby delaying the onset of the laminar vortex shedding regime. Although similar stabilization also occurs in shear-thickening fluids, this relationship is complex for shear-thinning fluids. Depending upon the degree of shear-thinning, the walls may stabilize or destabilize the flow. Extensive results are presented on streamline, vorticity contours and pressure profiles herein. The power-law behavior exerts significant influence on the macroscopic momentum transfer characteristics also. Thus, the drag and lift coefficients and Strouhal number exhibit complex dependence on Reynolds number, blockage ratio and power-law index. Finally, the present results are consistent with the limited data available in the literature.